JPH11224795A - Method and apparatus for generating plasma, plasma-applied surface treatment method and gas treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems attributable to the charge-up in generating the plasma, to smoothly generate the plasma with simple constitution at a low cost, and stabilize the plasma for a long time. SOLUTION: The plasma is generated by generating the alternating voltage to represent the pulse waveform using a high-voltage DC power supply and an inverter power supply 11 having a small switching circuit, and applying the alternating voltage to a pair of electrodes 6 arranged opposite to each other. A control means 19 to keep the plasma condition at the prescribed target condition based on the signal from a light intensity detecting means 15, a current value detecting means, or an impedance detecting means, is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma generation method,
The present invention relates to a plasma generation apparatus, a plasma-based surface treatment method, and a plasma-based gas treatment method, and more particularly, to a technique for generating plasma using an alternating electric field having a pulse waveform as an excitation source, and an application technique thereof.

[0002]

2. Description of the Related Art In recent years, the use of plasma has been promoted in various fields. As a method of generating this kind of plasma, a sine wave voltage such as a high frequency wave or a microwave is generally used. Is applied to a pair of electrodes arranged opposite to each other. This type of plasma generating apparatus is generally used in combination with a high-performance vacuum apparatus. Therefore, it is said that plasma needs to be generated in a relatively high-vacuum atmosphere. Was.

On the other hand, as a modified specific example of this type of plasma generation method, for example, according to Japanese Patent Application Laid-Open Nos. 61-149486 and 62-50472, a high-frequency voltage for plasma generation is applied to an electrode. Is applied in a pulse form. However, all of the techniques disclosed in these publications apply a high-frequency voltage intermittently, in other words, apply a pseudo pulse signal in which one pulse is formed as a sine wave voltage of a plurality of frequencies. Then, basically, a plasma is generated using a sine wave voltage in the same manner as in the above case.

[0004]

By the way, in the above-described conventional plasma generation method, since the supply voltage to the electrodes has a sinusoidal waveform, the energy efficiency of the power supply actually contributing to the plasma generation is extremely reduced. The problem arises. As a result, the power consumption increases, and a cooling device or the like for suppressing the generation of heat is separately required, which greatly hinders energy saving.

Further, when a sine-wave voltage is used for generating plasma as in the above-described conventional technique, a portion of the voltage between the pair of electrodes is concentrated due to the gradual rise of the voltage. When an electric field is generated, the insulating property at the location is locally reduced, so that only the location is activated with respect to the generation of plasma, and the generation of uniform plasma between the electrodes is inhibited. in addition,
According to this kind of sine wave voltage, since the fall of the voltage is gradual, the plasma once generated is not instantaneously lost, and due to this, the state of the plasma characteristic becomes unfavorable. There is also a problem that arc plasma is easily generated.

[0006] The arc plasma has a characteristic that it is difficult to be generated in an atmosphere having a high degree of vacuum.
In order to prevent the generation of the arc plasma, an extremely high-performance vacuum device, for example, a vacuum device equipped with an expensive turbo-molecular pump or the like is required, which leads to complication of the device and an increase in cost thereof. .

Further, the above-mentioned conventional plasma generation technology dislikes the use of an extremely inefficient power supply circuit or the like as an electrical component for generating a pulse, and the circuit configuration is downsized and simplified. No measures have been taken to achieve such a problem, and this not only causes a further increase in the complexity and size of the plasma generating apparatus, but also causes a problem of further increasing the cost. .

[0008] In addition, according to the above-described conventional plasma generation method, for example, when the surface state of an object to be processed made of an existing material or the like is to be modified by exposing the surface to plasma, the sinusoidal shape is required. DC positive or negative bias voltage for the purpose of compensating for the shortage of the voltage value due to the decrease in the fluctuation of the wave voltage and the shortage of the electric adhesion force and the electric processing force to the surface of the object to be processed due to the shortage. In this method, particles having negative or positive charges related to the treatment are caused to collide with the surface of the treatment object by electrostatic force. However, when such processing is continuously performed, the surface of the object to be processed is covered with only negative charges or only positive charges.
This causes a zip-up phenomenon. And, due to this, not only the surface state cannot be smoothly modified, but also the generation of uniform plasma is hindered,
This causes a problem that the generation of plasma itself is hindered. Such a problem is conspicuous when the surface of the object is formed of an insulating material.

In order to solve the problem of charge-up, for example, according to Japanese Patent Application Laid-Open No. Hei 8-92765, charge-up damage is caused by applying a positive high-frequency voltage to an electrode in a pulsed manner. There is a description that suppresses. However, if only a positive voltage is applied for plasma generation as in this publication, there is a possibility that the surface of the object to be processed may be covered with only negative charges, and the adverse effect due to charge-up is completely avoided. In this case, the voltage for generating plasma is a pseudo-pulse signal obtained by pulsing a high frequency wave itself. Occurs. Further, for example, Japanese Patent Application Laid-Open No. 8-13977 discloses a configuration in which a bias voltage having a pulse waveform is applied to an object to be processed, so that adverse effects due to electron shading, that is, charge-up, are removed. . However, in the technology disclosed in this publication, a pulse signal is applied as a bias voltage for preventing charge-up, whereas a microwave generated by a magnetron is used as a voltage for plasma generation. A voltage obtained by utilizing the voltage, that is, a voltage having a sine waveform is applied. Therefore, although the technology disclosed in this publication can be expected to suppress the adverse effects due to charge-up, the same problems as those listed above due to the fact that the voltage for plasma generation has a sine waveform may occur. In addition, a power supply device for preventing charge-up,
There is also a problem that two electric systems are required, including a power supply device for plasma generation, and the power supply device and, consequently, the size and complexity of the plasma generation device must be increased.

Further, according to the conventionally known apparatus for plasma generation, no consideration is given to the fact that the state of the plasma actually generated is always maintained at the target state. Therefore, the plasma state may be changed to an undesired state during the generation, and the plasma state may not be stable for a long time.

The present invention has been made in view of the above circumstances, and eliminates the adverse effects of plasma generation caused by charge-up by a single power supply device, and has a very simple configuration for generating uniform plasma. An object of the present invention is to provide a low-cost and high-quality plasma that can be generated even in a low vacuum or in the air, and to stabilize the plasma for a long time.

[0012]

Means for Solving the Problems A plasma generation method, a plasma generation apparatus, a plasma-based surface treatment method, and a plasma-based gas treatment method according to the present invention have the following configurations in order to achieve the above-mentioned technical problems. It is characterized by having done.

That is, the invention according to the plasma generating method described in claim 1 of the present application uses a high-voltage DC power supply and an inverter power supply having a small-sized switching circuit to generate an alternating voltage having a pulse waveform and to face each other. A plasma is generated by applying the alternating voltage to a pair of electrodes arranged in the plasma.

According to a second aspect of the present invention, there is provided an inverter power supply having a high-voltage DC power supply and a small switching circuit and generating an alternating voltage having a pulse waveform, and a small switching circuit for the inverter power supply. And a pair of electrodes which are electrically connected to each other and are arranged in a facing manner with a predetermined distance therebetween.

According to a third aspect of the present invention, there is provided an inverter power supply having a high-voltage DC power supply and a small switching circuit and generating an alternating voltage having a pulse waveform, and a small switching circuit for the inverter power supply. A pair of electrodes which are electrically connected to each other and are disposed opposite to each other at a predetermined distance, and light intensity detecting means for detecting the light intensity of plasma generated by applying the alternating voltage to the electrodes. And control means for controlling at least one of the voltage value, frequency and duty ratio of the alternating voltage based on a signal from the light intensity detecting means.

According to a fourth aspect of the present invention, there is provided an inverter power supply having a high-voltage DC power supply and a small switching circuit and generating an alternating voltage having a pulse waveform, and a small switching circuit for the inverter power supply. A pair of electrodes which are electrically connected to each other and are disposed opposite to each other with a predetermined distance therebetween, current value detecting means for detecting a current value flowing between the electrodes, and a signal from the current value detecting means. And control means for controlling at least one of the voltage value, frequency and duty ratio of the alternating voltage.

According to a fifth aspect of the present invention, there is provided an inverter power supply having a high-voltage DC power supply and a small switching circuit and generating an alternating voltage having a pulse waveform, and a small switching circuit for the inverter power supply. A pair of electrodes which are electrically connected to each other and are disposed opposite to each other with a predetermined distance therebetween, impedance detecting means for detecting impedance between the electrodes, and the alternating voltage based on a signal from the impedance detecting means. And control means for controlling at least one of the voltage value, the frequency, and the duty ratio.

According to a sixth aspect of the present invention, there is provided a plasma-assisted surface treatment method using the method according to the first aspect or the apparatus according to the second, third, fourth, or fifth aspect. By exposing the surface of a polymer material or a ceramic material to plasma, the state of the surface is modified.

According to a seventh aspect of the present invention, there is provided a plasma-assisted surface treatment method which is produced using the method according to the first aspect or the apparatus according to the second, third, fourth or fifth aspect. By exposing the surface of the metal material to the plasma, a thin film is formed on the surface.

The invention according to a plasma-based surface treatment method according to claim 8 of the present application is produced by using the method according to claim 1 or the apparatus according to claims 2, 3, 4 or 5. By exposing the surface of the living body substitute or the living body wearing article to the plasma, the hydrophilicity of the surface is improved.

The invention according to the plasma-based surface treatment method according to the ninth aspect of the present invention is produced by using the method according to the first aspect or the apparatus according to the second, third, fourth or fifth aspect. The surface of the contaminant is exposed to the plasma to disinfect the surface.

According to a tenth aspect of the present invention, there is provided a plasma-assisted gas processing method which is produced by using the method of the first aspect or the apparatus of the second, third, fourth or fifth aspect. By introducing a harmful gas into the plasma, harmful components contained in the gas are reduced or removed.

[0023]

According to the plasma generating method of the present invention, an inverter power supply having a high-voltage DC power supply and a small switching circuit is used, and the small switching circuit is, for example, a MOSFET element or a TTL.
It can be composed of a small semiconductor element such as an element.
When the inverter power supply having such a configuration is used, not only the power consumption can be reduced, but also the control of voltage and current can be performed only by switching. Therefore, the configuration of the electric circuit for plasma generation is extremely simplified and downsized, and the number of parts can be reduced and the cost can be reduced.

Further, since the voltage for generating plasma obtained by the inverter power supply has a pulse waveform, the energy efficiency of the power supply is improved as compared with the conventional sine wave voltage, and accordingly, the energy efficiency is further increased. Since the power consumption is reduced and the amount of generated heat is reduced, it is not necessary to separately provide a cooling device or the like, and it is possible to avoid an increase in the size and complexity of the entire device.

Further, since the voltage for generating plasma has a pulse waveform, the insulation between the pair of electrodes is impaired uniformly over a wide range due to the instantaneous rise of the voltage. Thus, uneven distribution of plasma due to local concentration of an electric field can be avoided, and uniform plasma can be generated between the electrodes.

In addition, since the pulse voltage of this type falls instantaneously, the plasma once generated is also instantaneously extinguished, so that arc plasma is not generated. As a result, a high-vacuum atmosphere for preventing the generation of arc plasma is not required, and it is possible to generate plasma satisfactorily even in a low vacuum or in the atmosphere. Need not be provided, it is sufficient to provide only an inexpensive rotary pump or the like, and the cost of the vacuum apparatus can be reduced.

Since the pulse voltage rises and falls instantaneously as described above, for example, when the surface modification of an object to be processed is performed using plasma generated by the pulse voltage. In such a case, a constant voltage value can always be secured while a voltage is applied, and the voltage value fluctuates and decreases as in a conventional sine wave voltage to reduce required electric adhesion, electric processing power, and the like. There is no situation in which it cannot be ensured, so that there is no need to separately apply a bias voltage.

Further, the polarity of the voltage is inverted at a predetermined cycle by performing the above-described switching, and the object to be processed is exposed to the plasma generated based on the alternating voltage thus obtained. However, since the polarity of the applied voltage is repeatedly inverted, only positive charges or only negative charges do not accumulate on the surface of the object to be processed, which leads to a charge-up phenomenon and various adverse effects associated therewith. Is avoided. Note that such a phenomenon is particularly effective when at least the surface of the object to be processed is formed of an insulating material.

The driving by the alternating voltage obtained only by the switching as described above is different from the driving by the ordinary sine-wave voltage with an ohmic loss as in the prior art, and it naturally possesses high energy efficiency. By devising switching control, it is possible to obtain output signals of various waveforms having an arbitrary frequency, and to ensure high controllability.

Incidentally, the voltage value of the alternating voltage obtained by the switching is 10 V to 1 MV peak-to-peak,
Preferably 100 V or more, more preferably 300 V to 1
0 KV, and the frequency is 0.1 Hz to 10 Hz.
GHz, preferably 100 Hz to 1 MHz, more preferably 1 KHz to 100 KHz.

The present invention according to claim 2 relates to a plasma generating apparatus comprising an inverter power supply having the same configuration as that described above, and a pair of electrodes connected to the inverter power supply. is there. Therefore, also in this case,
The same operation and effect as those of the first aspect can be obtained.

According to the plasma generating apparatus of the third aspect, in addition to the configuration of the apparatus of the second aspect,
Light intensity detecting means for detecting the light intensity of the plasma, and control means for controlling at least one of the three kinds of variable elements of the alternating voltage based on a signal from the detecting means. . Specifically, the control unit is configured to control the voltage value of the alternating voltage based on a signal from the light intensity detection unit,
At least one of the frequency and the duty ratio is controlled. That is, feedback control is performed so that the light intensity of the plasma is always constant, for example. If the light intensity of the plasma is constant as described above, the state of the plasma is also maintained at a constant state. Therefore, it is necessary to perform the feedback control while appropriately changing the three types of variable elements as described above. As a result, it is possible to avoid such a problem that the light intensity changes unexpectedly while the plasma is being generated and the plasma becomes unstable, and the plasma can be maintained in a desired stable state for a long time. become. As the light intensity detecting means, for example, a photodiode is used.

According to the fourth aspect of the present invention, when performing the feedback control for stabilizing the state of the plasma, the current value flowing between the pair of electrodes is detected by the operation of the current value detecting means. The control means controls at least one of the three types of variable elements in the same manner as described above so that the current value is always constant, for example. If the value of the current flowing between the electrodes is constant in this manner, it can be determined that the state of the plasma is also maintained in a constant state. It can be maintained in a state. Note that, for example, an ammeter is used as the current value detecting means.

According to the fifth aspect of the present invention, when performing feedback control for stabilizing the state of plasma, the impedance between the pair of electrodes is detected by the operation of the impedance detecting means. For example, the control means controls at least one of the three types of variable elements in the same manner as described above so that is always constant. If the impedance between the electrodes is constant in this way, it can be determined that the state of the plasma is also maintained in a constant state, so that the plasma is always brought to a desired stable state as in the case of the above-described claim 3. It can be maintained. As the impedance detecting means, for example, both an ammeter and a voltmeter are used.

According to the plasma-based surface treatment method described in the sixth aspect, the surface of a polymer material such as a plastic sheet or a plastic part is included in the plasma generated by using the above-described invention method or invention apparatus. Alternatively, the surface of the ceramic material is exposed, thereby modifying the surface state of the polymer material or the ceramic material.

The specific method for modifying the surface state in this case will be described in detail. For example, when a gas containing a fluorine element is turned into a plasma and the surface of a plastic sheet or the like is exposed to the plasma, The surface of the sheet is coated with fluorine, thereby obtaining a surface state rich in water repellency. Such an action can be similarly performed on the surface of various components made of a ceramic material.

Conversely, when a gas containing one or both of oxygen element and nitrogen element is converted into plasma and the surface of a plastic sheet or the like is exposed to the plasma, the water repellency deteriorates. As a result, a surface state rich in hydrophilicity is obtained. Because polymer materials are C and H
When this is exposed to, for example, a plasma of a gas containing elemental oxygen,
Although a chemical bond of C, O, and H is obtained, the surface of the polymer material in such a state has a characteristic of easily bonding to water molecules. Similarly, when a polymer material is exposed to a plasma of a gas containing a nitrogen element, a chemical bond of C, N, and H is obtained. Also has the property of being easily bonded to water molecules. In addition, when a polymer material is exposed to a plasma of a gas containing both oxygen and nitrogen, the chemical bond between C, O, and H and C,
Both the chemical bond of N and H are in a mixed state, and both of them have the characteristic that they are easily bonded to water molecules as described above. Such an operation can be performed basically in the same manner for various components made of a ceramic material. However, since ceramic materials do not originally contain H as a chemical bonding element, it is necessary to generate plasma in an atmosphere supplied with hydrogen gas, water vapor, or the like in order to obtain the same effect as described above. is there.

Further, another specific method will be described in detail. For example, an inert gas such as helium or argon is turned into plasma,
When the surface of a plastic part or the like is exposed to the plasma, the surface is randomly beaten by the kinetic energy, and a surface state having irregularities is obtained. Such a treatment can be effectively used as a pretreatment in a plating process of a plastic part,
The necessity of using chemicals is eliminated, and the simplification of the process by drying is promoted, and the problem such as contamination by waste liquid does not occur. The helium and argon exemplified above have an advantage that they can be easily converted into plasma and that they can be used safely and can be manufactured at low cost. It is possible to obtain the same effect as described above even if it is formed.

According to the plasma-assisted surface treatment method described in claim 7, a metallic material, for example, stainless steel, is contained in the plasma generated using the method and apparatus according to claims 1 to 5. The surface of steel, aluminum, or the like is exposed, thereby forming a thin film on the surface of the metal material.

The specific method of forming the thin film in this case will be described in detail. For example, a gas containing a carbon element, such as carbon dioxide, methane gas, ethane gas, ethylene gas, butane, or propane, is turned into plasma, and this plasma is formed. By exposing the surface of the metal material, a carbon thin film is formed on the surface. Further, when a gas containing a silicon element, such as silane gas, is turned into plasma and the surface of the metal material is exposed to the plasma, an amorphous silicon thin film is formed on the surface. Further, when a gas containing a boron element, such as decaborane, is turned into plasma and the surface of the metal material is exposed to the plasma, a thin film of boron is formed on the surface. in addition,
For example, when nitrogen gas is turned into plasma and the surface of the metal material is exposed to the plasma, the surface is subjected to a nitriding treatment. According to the above-listed techniques, surface characteristics excellent in abrasion resistance and the like can be obtained for any surface.

According to the plasma-assisted surface treatment method described in claim 8, a living body substitute or a living body is included in the plasma generated by using the method or apparatus according to any one of claims 1 to 5. It exposes the surface of the fitting, thereby improving the hydrophilicity of the surface of the replacement or fitting. In addition, an artificial bone, an artificial blood vessel, an artificial cornea, and the like can be cited as the living body substitute, and a contact lens (particularly, a disposable thing that has recently become popular) can be mentioned as the living body wearing article.

The specific method of the surface treatment in this case will be described in detail. For example, a gas containing one or both of oxygen element and nitrogen element is turned into plasma, and the surface of the living body substitute or the living body wearing article is put into the plasma. , A surface state rich in hydrophilicity can be obtained. The reason why the hydrophilicity is improved due to the presence of the oxygen element and the nitrogen element is as described above. In this case, considering the artificial bone (made of ceramics) among the biological substitutes, when connecting the artificial bone and the biological bone, if the artificial bone is rich in hydrophilicity, it will not be possible to connect the artificial bone to the biological bone. Adhesion or adhesion between them is improved, so that peeling hardly occurs, and the connection between the two is performed smoothly and firmly. Similarly, other biological substitutes are well connected to a living body because they are rich in hydrophilicity. In addition, for contact lenses among bio-wear products,
Since the hydrophilicity is improved and the water repellency is degraded, it does not easily peel off after mounting.

According to the plasma-based surface treatment method of the ninth aspect, the surface of a contaminant is included in the plasma generated by using the method and the apparatus according to the first to fifth aspects. Exposure, thereby disinfecting the surface of the contaminant. In addition, examples of the contaminants include instruments for medical use and the like used in a site where gene exchange is performed, and in particular, articles contaminated with organic substances such as proteins and DNA, and the like.

The specific method of the above-mentioned surface treatment in this case will be described in detail. Since this surface treatment method utilizes the thermal decomposition effect accompanying the heat treatment, the types of the elements contained in the gas to be plasmatized are as follows. You are not subject to strict restrictions. Then, by exposing the surface of the contaminant to plasma in an extremely high temperature state, proteins and DNA attached to the surface are thermally decomposed, thereby completing the disinfection. Therefore, it is not necessary to use, for example, a burner for incineration when attempting the heat treatment, and it is possible to perform the disinfection with a simple and compact configuration while also ensuring sufficient safety.

According to the plasma processing gas processing method according to the tenth aspect, the plasma generated by using the method and the apparatus according to the first to fifth aspects includes:
A harmful gas is introduced, thereby reducing or removing harmful components in the gas. Examples of the harmful gas include a gas discharged from an incinerator or the like and containing dioxin and NOx, and air contaminated at a site where gene exchange is performed.

The specific method of the gas treatment in this case will be described in detail. Since this gas treatment method also utilizes the decomposition effect caused by the heat treatment as in the case described above, the gas treatment to be converted into plasma is performed. For the types of contained elements,
You are not subject to strict restrictions. By exposing the dioxin to the plasma, the chemical bond between the benzene rings constituting the dioxin is cut off by the high heat of the plasma and decomposed, and then rapidly cooled to produce chlorine compounds. However, no harmful substances similar to dioxin are produced. Similarly, for NOx, the chemical bond between N and O is cut off by the high heat of the plasma and decomposed. On the other hand, when the contaminated air at the site of gene exchange is exposed to plasma, the proteins and DNA mixed in the contaminated air are thermally decomposed due to the heat treatment, and these harmful substances are removed. Become.

[0047]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a plasma generation method, a plasma generation apparatus, a plasma-based surface treatment method, and a plasma-based gas treatment method according to the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an appearance of a main body of a plasma generating apparatus according to an embodiment of the present invention. As shown in FIG. 1, a reaction chamber X of the plasma generating apparatus 1 includes a cylindrical tubular body 2, an upper lid body 3 that seals an upper part of the tubular body 2, and a lower part of the tubular body 2. Is formed as a space defined by a large-diameter lower lid 4 for sealing the lower lid 4, and three legs 5 projecting downward are fixed to an outer peripheral edge portion of the lower lid 4. . The tubular body 2, the upper lid 3 and the lower lid 4 are
It is made of a transparent acrylic resin material, so that the entire reaction chamber X inside can be observed.

At a substantially central portion of the reaction chamber X, a pair of electrodes 6 is disposed with a predetermined gap therebetween, and both electrodes 6 are provided with an insulating cover 7 made of Teflon or the like.
Are attached to the upper lid 3 and the lower lid 4 respectively. The surface portions of both electrodes 6 are covered with an insulating film 8 for making the plasma uniform. In this case, it is possible to use a glass plate, a ceramic plate, or the like instead of the insulating film 8, and even with these uses, the plasma can be made uniform. In this embodiment, at least one of the electrodes 6 is configured to be vertically movable such that the size of the gap between the two electrodes 6 is variable. This variable mechanism is not shown in detail, but, for example, a nut member having a female screw portion is fixed to the upper lid 3 and / or the lower lid 4, and a screw shaft having a male screw portion is fixed to the electrode 6 side. The nut member and the screw shaft are screwed and held so as to be relatively rotatable. In addition, the said cylindrical body 2
An inlet pipe 9 having a gas inlet into the reaction chamber X and an outlet pipe 10 having a gas outlet are attached to the peripheral wall of the reactor.

Each of the electrodes 6 is connected to a signal line a in a conductive state, and the signal line a is electrically connected to an inverter power supply.

As shown in FIG.
1 is basically a high voltage DC power supply 12 and a MOSFET
And a small switching circuit 13 composed of a semiconductor element such as an element. Then, the pair of switch switching sections 14 of the small switching circuit 13 is switched from the state of connection to the one side contact as shown in the figure to the state of connection to the other side contact to apply the voltage to the electrode 6. The polarity of the applied voltage is inverted. If necessary, a bias by a DC voltage may be applied to at least one of the electrodes 6.

The waveform of the voltage generated by the inverter power supply 11 may be, for example, one of the modes (a) to (d) shown in FIG.
It is an alternating voltage exhibiting a pulse waveform. The voltage value of the alternating voltage is preferably 100 V or more in a peak-to-peak manner. This means that it is necessary to secure a gap between the pair of electrodes 6 for interposing an object to be processed. Even when the object to be processed is, for example, a thin sheet or the like,
A gap of about 0.1 mm is required. Then, in the case where such a gap exists between the pair of electrodes 6, a voltage value of at least 100 V is required to generate plasma satisfactorily. Also, this voltage value is
More preferably, it is 300 V to 10 KV. This means that when the object to be processed is not a thin-walled one, the gap between the pair of electrodes 6 must be increased, and a good plasma is generated in a state where a gap corresponding to this is present. In this case, 300V or more is appropriate, while if it is 10KV or more, there is a tendency for the apparatus to be slightly larger.
Incidentally, if this voltage value is in the range of 10 V to 1 MV, a sufficient effect can be exhibited. This is 10V
If it is less than the above, it is not possible to generate plasma satisfactorily even if the gap between the electrodes 6 is made as narrow as possible, and if it is 1 MV or more, the apparatus becomes unnecessarily large.

On the other hand, the frequency of this alternating voltage is 100H
It is preferably z to 1 MHz. This is necessary to improve the plasma generation state and increase the processing speed appropriately.
This is because the frequency needs to be 00 Hz or higher, whereas if it is 1 MHz or higher, the effect of improving the energy efficiency of the inverter power supply cannot be sufficiently obtained. Further, the frequency of the alternating voltage is more preferably 1 KHz to 100 KHz. This is 1 KH to sufficiently increase the processing speed.
This is because the energy efficiency needs to be not less than z, and if it is not more than 100 KHz, the energy efficiency of the inverter power supply is appropriately improved. Note that this frequency is 0.1 Hz to 10 G
If it is in the range of Hz, a sufficient effect can be exhibited. This is a characteristic that if it is 0.1 Hz or less, it cannot function as an alternating voltage.
If the frequency is higher than GHz, the same operation and effect as those of the sine waveform can be obtained, and characteristics as an effective pulse waveform cannot be obtained.

As shown in FIG. 4, the plasma generating apparatus 1 according to this embodiment is provided as an additional element at a central portion on one side of the tubular body 2 and has a gap between the electrodes 6. A light intensity detecting means 15 such as a photodiode for detecting the light intensity in the vicinity, a voltage value changing circuit 16 for changing the voltage value of the alternating voltage generated by the inverter power supply 11, and a frequency of the alternating voltage And a duty ratio varying circuit 18 for varying the duty ratio of the alternating voltage. In addition, the plasma generating apparatus 1 includes a control unit 19 that controls the three types of variable circuits 16, 17, and 18 based on a signal from the light intensity detection unit 15. In this case, the variable circuits to be controlled by the control means 19 need not necessarily be three types as described above, and may be any one or two of them.

The control means 19 appropriately changes the voltage value, frequency and duty ratio of the alternating voltage based on the signal from the light intensity detection means 15 so that the light intensity of the plasma is always constant. In which feedback control is performed. If the light intensity of the plasma is constant in this manner, the state of the plasma is also maintained in a constant state. By performing the feedback control as described above, On the contrary, it is possible to avoid such a problem that the light intensity is changed to be in an unstable state and the plasma can be maintained in a desired stable state for a long time. In addition, a gas container 21 is connected to the introduction pipe 9 attached to the cylindrical body 2 via a flow meter 20.

As shown in FIG. 5, as another mode in which the control means 19 controls the three (or any one or two) variable circuits 16, 17, and 18, the light intensity detection means Instead of 15, a current value detecting means 22 such as an ammeter for detecting a current value flowing between the two electrodes 6 is provided. As still another aspect, instead of the current value detecting means 22, an impedance detecting means such as a combination of an ammeter and a voltmeter for detecting the impedance between the electrodes 6 is provided at a similar location. Be deployed. In this case as well, the control means 19 appropriately changes the voltage value, frequency, and duty ratio of the alternating voltage based on the signal from the current value detection means 22 or the impedance detection means, thereby providing a voltage between the two electrodes 6. The feedback control is performed such that the current value or the impedance of the current is always constant.

Next, the operation of the plasma generating apparatus 1 having the above configuration will be described.

First, the case where the surface treatment of a polymer material is performed by using the above-mentioned plasma generating apparatus 1 will be described.
A gas containing elemental fluorine is introduced into the reaction chamber X through the introduction pipe 9, and an alternating voltage having a pulse waveform is applied to the electrode 6 by the operation of the inverter power supply 11 to generate plasma. Then, by exposing the surface of the plastic sheet or plastic part to the plasma, a fluorine-coated water-repellent surface state can be obtained. On the other hand, when a gas containing an oxygen element and / or a nitrogen element is introduced into the reaction chamber X and turned into plasma in the same manner as described above, and the surface of the plastic sheet or the plastic part is exposed to the plasma, On the contrary, a surface state rich in hydrophilicity is obtained (the reason is as described above). Also, in the case where the ceramic material is subjected to surface treatment using the above-described plasma generation device 1, a surface state rich in water repellency or hydrophilicity can be similarly obtained. The surface of the ceramic material can be hardened by exposing it to a plasma of a gas containing a nitrogen element, a boron element, a carbon element, or a silicon element. Specifically, for nitrogen, the surface of the ceramic material is subjected to a nitriding treatment, whereas for boron, carbon, or silicon, these thin films are formed on the surface of the ceramic material.

When an inert gas such as helium or argon is introduced into the reaction chamber X and turned into plasma, and the surface of a plastic sheet or a plastic part is exposed to the plasma, the plasma has The surface is randomly beaten by kinetic energy,
As a result, a surface state having irregularities that can be effectively used for pretreatment in the plating step is obtained.

On the other hand, the case where the surface treatment of a metal material is performed by using the above-mentioned plasma generating apparatus 1 will be described. A gas containing a carbon element is introduced into the reaction chamber X and turned into plasma.
By exposing the surface of stainless steel, steel, aluminum or the like to this plasma, a carbon thin film is formed on the surface. Further, when a gas containing a silicon element is introduced into the reaction chamber X and turned into plasma, and a surface of stainless steel, steel, aluminum, or the like is exposed to the plasma, a thin film of amorphous silicon is formed on the surface. Further, when a gas containing a boron element is introduced into the reaction chamber X and turned into plasma, and a surface of stainless steel, steel, aluminum, or the like is exposed to the plasma, a boron thin film is formed on the surface. In addition, when nitrogen gas is introduced into the reaction chamber X and turned into plasma, and the surface of stainless steel, steel, aluminum or the like is exposed to the plasma, the surface is subjected to a nitriding treatment.

A case in which a surface treatment of a living body substitute or a living body attached article is performed using the above-described plasma generation apparatus 1 will be described. By exposing the surface of an artificial bone, an artificial blood vessel, an artificial cornea, a contact lens, or the like to the plasma, a highly hydrophilic surface state can be obtained (the reason is as described above). Although the artificial blood vessel is formed of a polymer material, the inner surface of the artificial blood vessel is exposed by exposing the inner surface of the artificial blood vessel to a plasma of a gas containing a carbon element to form a carbon thin film on the inner surface. It also has the advantage of smoothing and improved antithrombotic properties.

Further, a case where surface treatment of contaminants is performed using the above-described plasma generating apparatus 1 will be described. Any type of gas is introduced into the reaction chamber X without restriction, and plasma is generated. When the surface of the contaminant is exposed to the plasma, organic substances such as proteins and DNA adhered to the surface are thermally decomposed, and the surface is disinfected.

In addition, the case of removing NOx and dioxin contained in exhaust gas from an incinerator or the like using the above-mentioned plasma generating apparatus 1 will be described. At the end, a plasma generator 1 having basically the same configuration as that shown in FIG. 1 is attached. In this case, the configuration is such that the exhaust gas always passes through the plasma generated by the plasma generation device 1. With such a configuration, NOx or dioxin is thermally decomposed by introducing any gas of any type into the reaction chamber X and converting it into plasma, and exposing the exhaust gas to the plasma in this high temperature state. As a result, the harmful components in the exhaust gas are reduced or removed.

In addition, organic substances and D in contaminated air discharged from the site of gene exchange using the above-described plasma generating apparatus 1
Explaining the case of removing NA, first, a plasma generation device 1 having basically the same configuration as that shown in FIG. 1 is attached outside a ventilation fan such as a room where a gene exchange site is present. . In this case, the configuration is made so that the contaminated air released through the ventilation fan always passes through the plasma generated in the plasma generation device 1. With such a configuration, any kind of gas of unrestricted type is introduced into the reaction chamber X to be turned into plasma, and the exhaust gas is exposed to the plasma in a high temperature state, whereby organic substances and DNA are thermally decomposed. As a result, the harmful components in the contaminated air are reduced or removed.

As described above, the plasma generator 1 according to the present invention can be used for various surface treatments and gas treatments. High voltage DC power supply 12 and MOSFE
It is composed of a small switching circuit 13 such as a T element or a TTL element, and can be integrated, so that the device can be simplified, downsized, reduced in cost, and power consumption can be reduced. Will be. Further, since the voltage generated by the inverter power supply 11 is a voltage having a pulse waveform, the power supply efficiency is improved as compared with the conventional sine wave voltage, and further reduction in power consumption and no cooling device are required. Therefore, the size of the apparatus can be further reduced.

Further, since the pulse voltage generated by the inverter power supply 11 is an alternating voltage whose polarity is inverted at a predetermined cycle, the object to be processed is exposed to the plasma generated based on the alternating voltage. In addition, only the positive charges or only the negative charges are not accumulated on the surface of the object to be processed, and the adverse effects caused by the charge-up can be avoided. As a result, it is possible to easily generate good and uniform plasma as compared with the related art, and it is possible to perform a smooth process on the object to be processed.

In addition, since this type of pulse voltage rises instantaneously, the insulation between the pair of electrodes is impaired uniformly over a wide range, thereby causing local electric field concentration. Uneven distribution of plasma is avoided, and uniform plasma can be generated between the electrodes.

In addition, since this type of pulse voltage falls instantaneously, no arc plasma is generated, and a high vacuum atmosphere for preventing the generation of arc plasma is not required. Since plasma can be generated favorably even in a low vacuum or in the atmosphere, it is not necessary to provide an expensive turbo molecular pump or the like, and it is sufficient to provide only an inexpensive rotary pump or the like. In addition, since the above-described plasma-based surface treatment and plasma-based gas treatment can be performed in the atmosphere, gas treatment and the like, which were conventionally difficult or impossible, can be easily performed. Cost can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an appearance of a main body of a plasma generating apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic circuit diagram showing an inverter power supply of the plasma generation device according to the embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating characteristics of a pulse voltage generated by an inverter power supply of the plasma generation apparatus according to the embodiment of the present invention.

FIG. 4 is a schematic diagram showing an overall configuration of a plasma generating apparatus according to an embodiment of the present invention.

FIG. 5 is a schematic diagram showing an overall configuration of a plasma generating apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma generation apparatus 6 Electrode 11 Inverter power supply 12 High voltage DC power supply 13 Small switching circuit 15 Light intensity detection means 19 Control means 22 Current value detection means (impedance detection means)

Claims (10)

[Claims] An alternating voltage having a pulse waveform is generated by using a high-voltage direct-current power supply and an inverter power supply having a small switching circuit, and the alternating voltage is applied to a pair of electrodes arranged opposite to each other. A plasma generation method characterized by generating a plasma by performing the method. 2. An inverter power supply having a high-voltage DC power supply and a small switching circuit and generating an alternating voltage having a pulse waveform, and an opposing power supply electrically connected to the small switching circuit of the inverter power supply and separated by a predetermined distance. And a pair of electrodes arranged in the plasma generator. 3. An inverter power supply having a high-voltage DC power supply and a small switching circuit and generating an alternating voltage having a pulse waveform, and an opposing power supply electrically connected to the small switching circuit of the inverter power supply and separated by a predetermined distance. A pair of electrodes, a light intensity detecting means for detecting the light intensity of plasma generated by applying the alternating voltage to the electrodes, and the alternation based on a signal from the light intensity detecting means. A plasma generating apparatus, comprising: control means for controlling at least one of a voltage value of a voltage, a frequency, and a duty ratio. 4. An inverter power supply having a high-voltage DC power supply and a small switching circuit and generating an alternating voltage having a pulse waveform, and an opposing power supply electrically connected to the small switching circuit of the inverter power supply and separated by a predetermined distance. A pair of electrodes, a current value detecting means for detecting a current value flowing between the electrodes, and a voltage value, a frequency, and a duty ratio of the alternating voltage based on a signal from the current value detecting means. And a control means for controlling at least one of them. 5. An inverter power supply having a high-voltage DC power supply and a small switching circuit and generating an alternating voltage exhibiting a pulse waveform, and an opposing power supply electrically connected to the small switching circuit of the inverter power supply and spaced apart by a predetermined distance. A pair of electrodes, impedance detecting means for detecting impedance between the electrodes, and at least one of a voltage value, a frequency, and a duty ratio of the alternating voltage based on a signal from the impedance detecting means. A plasma generating apparatus, comprising: a control unit for controlling one of the two. 6. The method according to claim 1 or claim 2,
A plasma characterized in that a surface of a polymer material or a ceramic material is exposed to plasma generated by using the apparatus described in 3, 4, or 5, thereby modifying the state of the surface. Use surface treatment method. 7. The method according to claim 1 or claim 2,
A plasma-based surface treatment method, wherein a thin film is formed on a surface of a metal material by exposing the surface of the metal material to plasma generated by using the apparatus according to 3, 4, or 5. 8. The method according to claim 1 or claim 2,
By exposing the surface of a living body substitute or a living body wearing article to plasma generated using the apparatus described in 3, 4, or 5, the hydrophilicity of the surface is improved. Surface treatment method using plasma. 9. The method according to claim 1 or claim 2,
A surface treatment method using plasma, wherein the surface of the contaminant is disinfected by exposing the surface of the contaminant to plasma generated by using the apparatus according to 3, 4, or 5. 10. A harmful gas is introduced into a plasma generated by using the method according to claim 1 or the apparatus according to claim 2, 3, 4, or 5, whereby the harmful gas is contained in the gas. A gas processing method using plasma, wherein a harmful component is reduced or removed.